/Engine/Plugins/Runtime/RigVM/Source/RigVM/Public/RigVMCore/RigVM.h
The RigVMParameter define an input or output of the RigVM. Parameters are mapped to work state memory registers and can be used to set input parameters as well as retrieve output parameters.
[USTRUCT](Programming/UnrealArchitecture/Reference/Structs)([BlueprintType](Programming/UnrealArchitecture/Reference/Structs/Specifiers/BlueprintType)) struct FRigVMParameter